1. Field of the Invention
This invention relates in general to rail freight cars, and in particular to an improved bolster for a rail freight car truck.
2. Description of the Prior Art
Conventional freight rail cars are supported on rails by two trucks or wheel carriages. Each truck has two side frames, with a pair of wheels supported in each side frame. The side frames extend longitudinally, parallel with the rails. A bolster extends between the side frames. The bolster supports the car body and mounts to the side frames. The bolster has outer ends which extend through openings in the side frames. Coil springs also locate in the openings, allowing vertical movement of the bolster relative to the side frames to accommodate irregularities in the rail surface. The side frames have wear plates in the interior of the opening which are engaged by friction blocks on the bolsters in rubbing contact as the bolster outer ends move up and down with movement of the coil springs. The wear plates also have exterior portions located on the inner and outer sides of the side frame.
The bolster has four gibs on each outer end. The gibs are located on each opposite vertical side member, one on each side of the pocket and the bolster. The gibs are solid metal bars positioned to come into contact with the exterior portions of the wear plates due to relative lateral movement between the side frames and the bolster. A selected clearance or gap between the gibs and the wear plates of the side frame will be provided. Relative lateral movement causes the gibs, however, to come into contact with the side frame wear plates from time to time. Eventually, the gibs become worn out of tolerance and need to be replaced.
Where replacing the gibs, the worn gibs are ground off the bolster and new gibs are welded to the vertical sides of the bolster on each side of each pocket. A gage is employed to ensure that the distance between the gibs is accurate. In the prior art, the replacement gibs are solid metal forgings. The forging process produces a seam, which is a flat protruding band that extends longitudinally around the perimeter of the gib. In the prior art, the forging process results in the seam extending in a plane that is perpendicular to the gage side of the gib. The gage side of the gib faces the gib on the opposite the pocket. The seam thus extends through the gage side of the gib. This produces an irregular surface making it difficult to achieve the proper gage. The gage surface would need to be ground smooth first. This results in additional manufacturing expense.